1. Field of the Invention
This invention relates to improvements in wheelchairs and similar movable objects and, more particularly, to a stair-climbing wheelchair having means for cushioning the movements of the wheelchair as it moves from an inclined position to a horizontal position or from a horizontal position to an inclined position.
2. Description of the Prior Art
An improved wheelchair for climbing stairs and inclined ramps has been described in U.S. Pat. No. 4,564,080. The wheelchair has ground-engaging wheels and a pair of endless flexible tracks which are alternately in engagement with the surface below the wheelchair. Thus, the wheelchair can be movable along a horizontal path when the wheels engage the ground and can be moved along an inclined path, such as a stairway or a ramp, when the tracks are in engagement with the surface. The wheels and tracks are motor driven and suitable controls are provided to allow for forward and reverse movements of the wheelchair as well as for turning movements of the wheelchair.
In U.S. Pat. No. 4,671,369, an improvement for the wheelchair has been described wherein a pair of cushioning arms and fluid piston and cylinder assemblies operate to avoid rapid downward movements of the front and the rear of the wheelchair as the wheelchair moves from a horizontal path to an inclined path or from an inclined path to a horizontal path. The arms which effect the cushioning of the wheelchair often drag on the surface below the wheelchair as the wheelchair moves along the surface. It would be desirable to control the positions of the arms when the arms are not in use for cushioning purposes, i.e., when the wheelchairs move over a horizontal surface. Thus, a need exits for improvements in the controlling of the positions of the arms of a wheelchair of the type described and the present invention satisfies this need.